Aerosol dispensing system

ABSTRACT

An aerosol dispensing system having an outer container, compressible inner container positioned within the outer container, means to compress the compressible container, and a mechanical breakup spray head and valve assembly connected to the compressible container. A relatively non-foaming liquid product is present at a pressure above atmospheric pressure within the compressible container as well as a neutral propellant or mixture of propellants which are in a liquid state and are at least partially soluble or miscible in the liquid product. A second propellant may be present in a propellant region between the compressible container and outer container with the second propellant exerting a differential pressure across the compressible container which is sufficient to eject the product and neutral propellant through the mechanical breakup spray head on opening of the valve assembly. The neutral propellant is present in a relatively small amount, e.g., about 25 percent or less by volume of the volume of the product and neutral propellant and generally about 10 percent or less with the neutral propellant being at least partially vaporized at atmospheric pressure or less on passage of the product and neutral propellant through the spray head to create a turbulence within the spray head which provides a breaking up of the liquid product into a fine spray. 
     An aerosol dispensing system with a mechanical breakup spray head and valve assembly connected to compressible container positioned within an outer container with a finely divided powder product at a pressure above atmospheric pressure within the container. Also present within the compressible container is a liquified neutral propellant in an amount sufficient to form a slurry with the product and to carry the product into the spray head during discharge of the product. The neutral propellant is at least partially vaporized at atmospheric pressure or less on passage of the product and neutral propellant through the spray head to create turbulence within the spray head.

RELATED APPLICATIONS

This application is .Iadd.a reissue of my U.S. Pat. 3,938,708 which wasfiled as U.S. Application Ser. No. 544,390 on Jan. 27, 1975 which is.Iaddend.a continuation-in-part of my prior .[.copending.]. applicationSer. No. 497,613, filed Aug. 15, 1974 now abandoned, which is in turn acontinuation-in-part of my .[.copending.]. application Ser. No. 466,140,entitled "AEROSOL DISPENSING ARRANGEMENT" which was filed on May 2,1974, now abandoned.

BACKGROUND OF THE INVENTION

A wide variety of products are now packaged for dispensing as a finelydivided aerosol spray. For example, such products include hair sprays,deodorants, food products, etc. While many products have beensuccessfully dispensed as aerosols, a wide variety of products are,however, not amenable to being dispensed in this manner.

By way of background, in dispensing a product as an aerosol, the productwhich is usually in the form of a liquid, is placed within apressurizable container and a propellant is then added to the product.Then, during dispensing of the product as an aerosol, the mixture ofproduct and propellant is discharged from the container through a spraynozzle with the product being discharged in the form of a fine spray.

In general, there are two main types of propellants which may be usedfor aerosol systems, these being hydrocarbon propellants and halogenatedhydrocarbon propellants. Both types of propellants have their drawbacksand, thus, in practice the particular propellant which is employed for aparticular application is dictated by the nature of the product which isbeing dispensed.

To generate the pressure required to dispense a product in the form ofan aerosol, the propellant must, in general, be present in a sufficientamount in admixture with the liquid product to carry the product throughthe spray head and to generate an internal pressure within the productcontainer to accomplish this, e.g., generally about 30 psig or higher.The particle size of the product, after its discharge through a sprayhead, is a function of the viscosity of the product and also thepressure generated by the aerosol propellant. In general, as theviscosity of the product is increased, the size of the product particlesdischarged through the spray head is increased. Conversely, as thepropellant pressure is increased, the size of the product particles isreduced.

Based on the above considerations, it might appear that any liquidproduct, no matter how viscous, could be packaged as an aerosol merelyby adding sufficient propellant to generate a driving force that wouldbe adequate to break up the product into a fine spray on discharge ofthe product through a spray head. In fact, however, the formulation of asuccessful aerosol system is complicated by a host of other factorswhich make it impossible to arrive at a satisfactory system merely byincreasing the internal propellant pressure to whatever level may bedictated by the viscosity of the product.

As a first consideration, many propellants are incompatible withspecific products at the relatively high propellant levels required togenerate the necessary propellant pressure for discharge of the productas a fine spray. For example, many aerosol systems require apropellant-to-product volume ratio of about 50:50 to generate asufficient propellant pressure to eject the product as a fine spray. Infact, some products, such as a frying pan spray, may require apropellant-to-product volume ratio of as high as about 95:5 to break upthe viscous vegetable oil product into a fine spray.

At high propellant levels, the internal pressure generated by thepropellant within an aerosol container may pose substantial safetyproblems unless the container is specially constructed to withstand highinternal pressures. The vapor pressure of the propellant will vary withthe ambient temperature which may be as high as 110° to 120° F. in someareas where the product is used. Even though an aerosol system isdesigned for an ambient temperature of about 70° F., the propellantcontainer must, therefore, be sufficiently strong to withstand thehigher pressures which are developed by the propellant at higher ambienttemperatures. The cost of the aerosol product will be determined, to alarge extent, by the cost of the aerosol container. Thus, if thepressure demands of an aerosol system require the use of an expensivehigh pressure aerosol container, the aerosol product may be economicallyunfeasible.

Further, as the propellant-to-product volume ratio is increased, theamount of product is reduced. This may make the aerosol productunattractive to the consumer who must then purchase a relatively largequantity of propellant to obtain a relatively small quantity of product.This situation is illustrated by aerosol frying pan sprays where theconsumer may have to purchase 95 percent by volume of propellant merelyto obtain 5 percent by volume of the product. Also, as thepropellant-to-product ratio is increased, the use life of the aerosolsystem is reduced due to the smaller quantity of the product which ispresent. This wll also make the aerosol product less attractive to theconsumer.

In addition to the economic problems which are posed by aerosol systemsthat require a relatively large amount of propellant, there may also becompatibility problems between the propellant and product at highpropellant-to-product volume ratios. For example, liquified hydrocarbonpropellants are generally incompatibile with water base paints at thehigher propellant-to-product volume ratios with the product forming agel which cannot be ejected through a mechanical breakup nozzle in theform of a line spray. Halogenated hydrocarbon propellants, such as theproducts sold by E. I. DuPont de Nemours under the trade name "FREON"also have compatibility problems with various types of products. Inorder for a propellant to be used with a particular product, thepropellant must be miscible, to some degree, with the product. However,halogenated hydrocarbon propellants are generally immiscible with waterbased products with the propellant and product forming separate layersand the propellant, thereby, not functioning to discharge the product asa fine spray through a spray nozzle.

In addition to compatibility problems, the use of a particularpropellant in a given aerosol system may create still further problems.Hydrocarbon propellants are generally flammable in air at higherconcentrations. Thus, when the driving force for the propellant systemrequires a high propellant-to-product volume ratio, a hydrocarbonpropellant will generally be unsuitable for reasons of safety.

Also, halogenated hydrocarbon propellants are generally toxic and mayform phosgene if contacted by flame. In addition, halogenatedhydrocarbon propellants are expensive. Because of their toxicity,halogenated hydrocarbon propellants are generally unsuitable for use inan ingestible food product.

Due to the various problems of cost, safety, compatibility,flammability, toxicity, etc., as enumerated above, certain types ofproducts are dispensed from containers in which the product isphysically separated from a propellant that is used to discharge theproduct from the container. These types of containers, which may betermed "barrier packs", are exemplified by the barrier pack sold underthe name "SEPRO" by Continental Can Company and that sold under thetrack name "POWER-FLOW" by American Can Company.

In a barrier pack, a flexible inner container for the product isprogressively collapsed by the pressure generated by a propellant in theregion between a rigid outer container and the flexible inner container.The product is, thereby, extruded through an opening leading from thecollapsible inner container. If the product being dispensed from abarrier pack container is a foamable product, such as a shaving cream,the liquid product within the flexible inner container may also containa propellant in admixture therewith. Then, when the product has beenextruded from the inner container, the propellant within the productwill undergo vaporization at ambient pressures to produce foam. Such anaerosol package is shown in the Lauwe patent, U.S. Pat. No. 3,788,521,dated Jan. 29, 1974.

The foregoing problems have sharply limited the usage of aerosoldispensing systems for various products and have generally precludedtheir use for products such as viscous water base products, ingestiblefood products, etc. Thus, it would be highly desirable to provide anaerosol dispensing system which would not be subject to the variousdrawbacks encountered with present aerosol systems and which could beused to dispense essentially any type of liquid or powdered productincluding viscous water base paints and ingestible food products.

SUMMARY OF THE INVENTION

In accord with the present invention, I have provided an aerosoldispensing system which is capable of usage with essentially any type ofproduct, including products such as high viscosity water base paintswhich previously could not be dispensed in the form of a fine spray byany known aerosol system. Through use of the aerosol dispensing systemof the invention, the problems which have long plagued the aerosolindustry, such as incompatibility of the product and propellant,flammability of the propellant, toxicity of the propellant, etc., havenow largely been eliminated.

In the aerosol dispensing system of the present invention, a liquidproduct is contained at a pressure above atmospheric pressure withincompressible container means within an outer container with thecontainer means preferably comprising a flexible or collapsible innercontainer as provided by a barrier pack dispenser. In admixture with theliquid product is a small quantity of a neutral gas (herein termed aneutral propellant) which is a liquid and is soluble or miscible to someextent in the product. A mechanical breakup spray head which generallyemploys a swirl zone having projections therein which impinge upon theproduct as it is moved rapidly through the swirl zone is connected tothe compressible container means while means are provided to compressthe compressible container means, e.g., a second propellant may bepresent in a propellant region bounded by the interor of an outercontainer and the exterior of a flexible inner container. The secondpropellant may be present in the propellant region in an amountsufficient to generate a pressure differential between the propellantregion and the flexible inner container of about 5 psig or higher, e.g.,15 or 30 psig or higher, which is sufficient to discharge the productwith the neutral propellant therein through a mechanical breakup spraynozzle on opening of a valve connecting the compressible container meanswith the spray nozzle.

On passage of the product through the mechanical breakup spray nozzle inthe present aerosol dispensing system, the neutral propellant is atleast partially vaporized at atmospheric pressure or less and itssolubility or miscibility in the product is reduced. This gassifies theneutral propellant within the mechanical breakup spray nozzle to provideadditional turbulence such that the product is broken up and issues fromthe spray nozzle as a finely divided spray.

The neutral propellant present in the product within the compressiblecontainer means is generally present in a small amount such as about 10percent by volume or less and preferably about 6 percent by volume orless although for some specific products, such as a heavy viscosityproduct where the neutral propellant acts as a solvent to decreaseviscosity, the neutral propellant may range up to about 25 percent byvolume. Desirably, the neutral propellant is soluble to some extent in aliquid state in the liquid product to decrease the viscosity of theliquid product. Also, the neutral propellant preferably has a vaporpressure of about 30 psig or higher but may be relatively low, e.g.,about 17 psig, depending on the nature of the product.

In another aspect of the invention, the product within the compressiblecontainer means is a powder such as aluminum chlorhydrate, talc, cornstarch, etc. When the product is a finely divided powder, the neutralpropellant may be present in a larger quantity than the generally 101percent or less used for a liquid product. With a product which is afinely divided powder, the neutral propellant is present in a liquidstate in a sufficient quantity to form a slurry with the powderedproduct and to, thereby, carry the finely divided powder into themechanical breakup spray head. As an example, the liquified neutralpropellant may, in the case of a powder product, be present in an amountup to about 25 percent or more by weight of the powder product. Alsopresent in a powder product may be an emolient oil, such as isopropylmyristate, which makes a powder product cling to the body.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more fully understood from the following detaileddescription taken together with the accompanying drawing wherein

FIG. 1 illustrates a preferrred embodiment of a dispensing arrangementaccording to the principles of the present invention.

DETAILED DESCRIPTION

Referring now to the drawing, there is illustrated an embodimentgenerally designated 10 of an aerosol dispensing system according to theprinciples of the present invention. The aerosol dispensing system 10 isgenerally comprised of a barrier pack container generally designated 12which includes a rigid outer container 14 and a flexible bag or bladder16 contained therein. Instead of using a flexible bag 16, other forms ofa compressible container means may be employed as a piston dispenser inwhich a piston is slidably received within a container with the productplaced on one side of the piston and means to compress the piston, suchas a spring means or a propellant, placed on the other side of thepiston. Also, the compressible container means may be a resilientlyexpandable bag which is formed of an elastic material such that the bagin its expanded condition exerts a compressive force on a product withinthe bag. The flexible bag or bladder 16 may be coupled to the rigidouter container 14 at the top 18 thereof in fluid tight sealingrelationship by crimping a mounting cup 20 thereon. The mounting cup 20is a part of a valve assembly 22 which includes a mechanical breakupspray head 24 through which the aerosol dispersion is dispensed.

Barrier pack containers are commercially available in various volumetricsizes and may be obtained, for example, from Continental Can Company,American Can Company, or other suppliers.

The valve assembly 22 is also commercially available from variousmanufacturers such as Precision Valve Corporation or Aerosol ResearchCompany. The dispensing head 24, in accordance with the principles ofthe present invention, is a mechanical breakup head which is alsoavailable as part of the valve assembly 22.

A second propellant generally designated 26 is contained between theflexible bag 16 and the rigid outer container 14 and may be retainedtherein by a stopper means 28 inserted in a fill aperture 30 in therigid outer container 14.

The product to be dispensed 32 is contained within the flexible bag 16.For example, the product to be dispensed may be a comparatively viscousingestible food product such as a vegetable oil which is dispensed as acomparatively fine spray from the dispensing head 24. According to theprinciples of the present invention, there is also a neutral propellantgenerally designated 34 contained within the flexible bag 16.

According to the principles of the present invention, the secondpropellant may be essentially any propellant such as Freon-12,chlorinated hydrocarbons, vinylchlorides, propane, isobutane, carbondioxide, or the like. In the system 10 shown in FIG. for example, amixture of isobutane and propane may be utilized as the secondpropellant 26 and such a mixture may have a vapor pressure, at 70° F.,in the range of 40 to 80 psig. Since the second propellant 26 does notcome in contact with the product 32 within bag 16, any propellant issatisfactory which is compatible with the structure of the barrier pack12.

The neutral propellant 34 must be miscible to some extent in the product32. Preferably, the neutral propellant 34 is sufficiently soluble in theproduct 32, in the case of a liquid product, to lower the viscosity ofthe product and to, thereby, make the product easier to eject throughthe dispensing head 24. For the reasons stated previously, theparticular neutral propellant 34 which is employed will be dependent onthe nature of the product 32. If the product 32 is a water base productor an ingestible food product, the neutral propellant 34 will generallybe a hydrocarbon, since halogenated propellants are generally notcompatible with water base products and their toxicity generallyprecludes their use in ingestible food products.

Suitable neutral propellants may include, for example, propane,isobutane, n-butane, hexane, and non-hydrocarbon gases such as nitrousoxide, carbon dioxide, nitrogen, and the like. The neutral propellantmay be in a liquified state mixture admixture with a liquid product or aportion of the neutral propellant may, for example, be present in theproduct in the form of a gas-in-liquid solution, particularly preferredneutral propellants for use in the present aerosol system are propane,isobutane, and n-butane since these propellants are generally approvedfor use in ingestible food products. Also, these propellants have, ingeneral, a reasonable solubility in a wide variety of liquid products.However, since the solubility of a neutral propellant in a liquidproduct will vary, depending on the particular nature of the liquidproduct, a particular neutral propellant or mixure of neutralpropellants may be chosen to optimize the solubility of the neutralpropellant or propellants in a particular product or to minimize theviscosity of the liquid product.

The product 32, if a liquid, is one which does not produce anyappreciable foaming on ejection through the dispensing head 24. Also,the content of neutral propellant 34 in a liquid product 32 is generallymaintained at a sufficiently low level to not produce bubbles in theproduct after it has been sprayed onto a surface of some kind throughthe dispensing head 24.

Depending on the nature of the product 32, the neutral propellant 34 mayalso be a halogenated hydrocarbon, i.e., the liquid product not being awater base product and not being an ingestible food product. If ahalogenated hydrocarbon or mixture of halogenated hydrocarbonpropellants is used as the neutral propellant, the neutral propellantpreferably have a relatively low vapor pressure, such as about 17 psigand preferably about 30 psig or higher. Thus, the second propellantpressure may be reasonably low while providing a sufficient differentialpressure to eject the product and neutral propellant through amechanical breakup spray head in producing a fine spray of the product.

Table I illustrates the characteristics of propane, isobutane and butaneas may be utilized for the second propellant 26 and also for the neutralpropellant 34. It will be appreciated, however, that while only propaneand isobutane have been listed in Table I, various mixtures thereof maybe obtained to achieve a vapor pressure anywhere between 31 and 107.8psig at 70° F., depending upon the second desired pressure for thepropellant 26 or neutral propellant 34. Further, as noted above, otherpropellant gases may equally well be utilized as the second propellant26.

                                      TABLE I                                     __________________________________________________________________________              Second Propellant                                                                           Neutral Propellant                                                            Hydrocarbon                                                     Hydrocarbon                                                                          Hydrocarbon                                                                          Propellant                                                      Propellant                                                                           Propellant                                                                           A-17                                                            A-108  A-31   Food Grade                                                                           Test                                           Property  Propane                                                                              Isobutane                                                                            Butane Method                                         __________________________________________________________________________    Composition, mol %                                                            Ethane    Trace  --     --     Chromoto-                                      Propane   99.3    .4    .08    graphy                                         Isobutane  .6    96.3   .8                                                    Normal Butane                                                                           --      3.2   98.54                                                 Pentanes  --     --     .48                                                   Total Saturates                                                                         min 99.9                                                                             min 99.9      Chromoto-                                                                     graphy                                         Vapor Pressure                 ASTM D-1267                                    psig at 70° F.                                                                   107.8  31.0   17.0   (mod. 70° F.)                           Sulfur, ppm                                                                             NIL    NIL    NIL    ASTM D-1266                                    Residue, g/100 ml                                                                       NIL    NIL    NIL    ASTM D-1353                                    Acidity of Residue                                                                      neutral                                                                              neutral                                                                              neutral                                                                              ASTM D-1093                                    Odor      pass   pass   pass   Panel                                          Water, ppm                                                                              0.0005 0.9995 0.0005 C.F.                                           __________________________________________________________________________

If desired, in order to further enhance the dispersion characteristicsof the product to be dispensed 32 contained within flexible bag 16, asurfactant may be added thereto. If the fluid product 32 is aningestible food, the surfactant must be non-toxic and substantiallyodor-free and taste-free. It has been found that a food grade surfactantsuch as polysorbate 80 USP available from Atlas Chemical Division is asatisfactory surfactant when utilized with, for example, vegetable oils.

The surfactant may be added to a fluid product in an amount sufficientto reduce the surface tension of the fluid to a desired level forspraying of the product, e.g., approximately 0.01 to 0.5 percent byweight of the product. The surfactant reduces the surface tension of thefluid to be dispensed 32 and thus allows dispensing of the fluid 32 in amuch finer dispersion spray.

When the above mentioned food grade butane is utilized as the neutralpropellant 34 mixed with a vegetable oil, it has been found thatmaintaining the ratio of butane to the fluid to be dispensed 32 atapproximately a maximum of one part by volume butane to seven parts byvolume fluid 32 provides satisfactory operation and yet is below theflammability limit for the butane.

Depending upon the viscosity of the fluid to be dispensed as well as thevapor pressure of the second propellant gas 26, the vapor pressure ofthe neutral propellant 34 may, for example, be in the range of about 5to about 40 psig or higher at 70° F., such as 3, or 50 psig.

When the fluid to be dispensed 32 is vegetable oil and the neutralpropellant 34 is the above described butane, the second propellant gas26 may be a mixture of isobutane and propane having a vapor pressure at70° F. of approximately 70 psig. This provides a differential pressureacross the flexible bag 16 of 53 psig.

In operation, when the valve assembly 22 is activated, the secondpropellant 26 squeezes the flexible bag 16 and the fluid 32 and neutralpropellant 34 are forced through the breakup head 24. In the mechanicalbreakup head 24, which may be described as a swirl chamber, the fluid isdirected into paths which supply centrifugal force to the fluid or othertypes of breakup arrangements may be utilized, and the fluid is thendispersed through the orifice of the head.

The neutral propellant which is present in the product 32 is at leastpartially vaporized within the breakup head 24. Also, the solubility ofthe neutral propellant 34 in the product 32 is reduced by the action ofthe mechanical breakup head 24 on the product 32. This providesgassification of the neutral propellant or propellants within thebreakup head 24 which produces a very high degree of turbulence to breakup the product into fine particles.

The product, if a liquid, is relatively non-foaming. Further, since theneutral gas or gases are present at a relatively low concentration inthe product, essentially all of the neutral propellant is evaporatedwithin the mechanical breakup spray head or shortly thereafter oncontact of the neutral propellant or propellants with the atmosphere.

As stated, the vapor pressure of the neutral propellant or mixture ofpropellants 34 is generally low since the function of the neutralpropellant is not to act as a primary propellant, such as the secondpropellant but rather is to vaporize within the mechanical breakup sprayhead 24 to assist in breaking up the product into smaller particleswhich exit from the spray head as a fine spray. Thus, the neutralpropellant or mixture of propellants 34 may have a vapor pressure of 0psig or lower so long as the neutral propellant or propellants arevaporized within the mechanical breakup spray head 24. As an example,n-butane has a vapor pressure of about 0 psig at about 50° F. and anaerosol dispensing system according to the invention using n-butane as aneutral gas functions at an ambient temperature of 50° F.

When the vapor pressure exerted by the neutral propellant is increasedto about 30 psig or higher, I have found that a lower differentialpressure may be employed across the flexible bag 16 in expelling theproduct through the high mechanical breakup spray head 24. Further, whenthe vapor pressure of the neutral propellant is increased, I have foundthat a lower quantity of neutral propellant may be used, depending uponthe particular nature of the product, in obtaining a fine spray throughthe high mechanical breakup spray head 24. To illustrate, when theneutral propellant is A-31 (as described in Table I), the quantity ofneutral propellant required in obtaining a fine spray for a particularproduct may generally be decreased from the amount of neutral propellantwhich is required if n-butane is employed as the neutral propellantsince the A-31 gas has a vapor pressure at standard conditions of about31 psig while n-butane has a vapor pressure at standard conditions ofabout 17 psig. Also, when A-31 gas is utilized as a neutral propellant,the differential pressure between the inside of the flexible bag 16 andthe propellant region outside the bag may generally be decreased fromwhat is required when n-butane is the neutral propellant.

Similarly, if the commercial gas A-46 is employed as a neutralpropellant (A-46 being a commercial blend of n-butane, isobutane andpropane having a vapor pressure under standard conditions of about 46psig), the quantity of neutral propellant may be decreased even furtherfrom the amount required when A-31 is the neutral propellant. Also,using A-46 as the neutral propellant, the differential pressure betweenthe interior of the bag 16 and the propellant region outside the bag maybe decreased even further.

In tests which were performed in the spraying of an anti-perspirantpowder, it was found that A-46 gas could be employed both as the neutralpropellant and also as the second propellant providing that a vapordepressant was admixed with the neutral propellant within flexible bag16. In this test, the vapor depressant which was added was ahalohydrocarbon (Freon-11, Freon being a trademark of E. I. DuPont deNemours & Company) with the vapor pressure suppressant being present inan amount sufficient to reduce the vapor pressure within the flexiblebag 16 by about 2 psig. The differential pressure across the flexiblebag 16 was, thus, in this case only about 2 psig.

The use of a neutral propellant having a higher vapor pressure such asabout 30 psig or higher, is particularly advantageous in an aerosoldispensing system in which the product is a finely divided powder.Through use of a neutral propellant having a higher vapor pressure,there is less clogging of the high mechanical breakup spray head by thefinely divided powder as it passes through the spray head. Further, theuse of a neutral propellant having a higher vapor pressure such as about30 psig or higher, provides a sprayed product which is essentially dryon contact with the skin of the user in the case of a personal product,e.g., an anti-perspirant powder. This is advantageous because thecontact of a wetted product with the user's skin, e.g., ananti-perspirant powder that is wetted with n-butane that has notvaporized, produces a cold sensation which many users may findundesirable.

The use of a neutral propellant which has a higher vapor pressure, suchas about 30 psig or higher at standard conditions of temperature andpressure, provides greater turbulence when the mixture of neutralpropellant and product (either a relatively non-foaming liquid or afinely divided powder) passes through the high mechanical breakup sprayhead. This is advantageous because the greater turbulence producedwithin the spray head by the gassification of the neutral propellant ismore effective in providing a product in the foam of a finely dividedspray.

Immediately after leaving the terminal orifice of the high mechanicalbreakup spray head, the neutral propellant undergoes evaporation withthe rate of evaporation being dependent upon the vapor pressure of theneutral propellant which may be altered by the presence of otherpropellants, such as a vapor pressure depressant, that may be present inminor amounts in conjuction with the major propellant component. Ingeneral, as the vapor pressure of the neutral propellant is increased,the neutral propellant will evaporate more rapidly after leaving theterminal orifice of the high mechanical breakup spray head. Throughrapid evaporation of the neutral propellant after leaving the terminalorifice of the high mechanical breakup spray head, the product maycontain little or no neutral propellant when it contacts the surface orobject against which it is being sprayed. This is advantageous in apersonal use product, as stated, since the product is in an essentiallydry state when it contacts the body of the user. Further, in a productsuch as a paint, the pressure of unevaporated neutral propellant withinthe paint after its contact with the surface to be painted may beundesirable since the evaporation of the neutral propellant may preventthe formation of a smooth painted surface.

Still another advantage which flows from the use of a neutral propellanthaving a higher vapor pressure, such as about 30 psig or higher understandard conditions, is a reduction in the flammability of the sprayedaerosol product. While flammability may be defined in several ways, oneway in which flammability of aerosols has been defined is in terms ofwhether the sprayed product is flammable at a distance of one foot fromthe terminal orifice of the spray head. Using this criteria forflammability, if the neutral propellant has a vapor pressure such asabout 17 psig in the case of n-butane, the neutral propellant may not becompletely evaporated within the time required for the sprayed productto traverse a distance of one foot from the terminal orifice and then-butane which is still evaporating will produce a flammable mixture.If, however, the neutral propellant has a higher vapor pressure thanthat of n-butane, the neutral propellant will be substantiallyevaporated from the sprayed propellant product within the first foot oftravel from the terminal orifice of the high mechanical breakup sprayhead. The neutral propellant will, then, not be present when the sprayedproduct contacts a flame source at a distance of one foot from theterminal orifice and the sprayed product will have a greatly reducedflammability.

A still further advantage of using a neutral propellant with a highervapor pressure is that its use may permit a marked reduction in thedelivery rate of the sprayed aerosol product. In accord with the presentinvention, a much higher content of product (whether a relativelynon-foaming liquid product or a finely divided powder product) may bepresent within the aerosol container as compared with previous aerosolproducts in which the propellant gas was mixed directly with theproduct. While this is advantageous because it is a more efficient meansof product delivery, the very efficiency of the system may createproblems in regard to the product delivery rate.

With a much greater quantity of product being present within the aerosolcontainer, the delivery rate may be many times that of a conventionalaerosol. This may be undesirable since it may result in dispensing amuch larger quantity of product through the high mechanical breakupspray head than is actually needed or desired by the user. By using aneutral propellant having a higher vapor pressure under standardconditions, such as about 30 psig or higher, a lower differentialpressure may be used between the interior of flexible bag 16 and theexterior of the flexible bag. This provides a reduction in the productdelivery rate with the reduction being proportional to the decrease inthe differential pressure across the flexible bag 16.

In spray testing an anti-perspirant powder while using n-butane as theneutral propellant, it was generally necessary to use a differentialpressure across the flexible bag 16 of about 30 psig with the deliveryrate of product and neutral propellant leaving the high mechanicalbreakup spray head being about 21/2 grams per second. When the neutralpropellant was then changed from n-butane to the commercial A-31 gas asdescribed previously, the differential pressure across the flexible bag16 could be reduced to about 15 psig while still providing a very finespray of the aerosol product. By reducing the differential pressureacross the flexible bag 16 from about 30 psig to about 15 psig, thedelivery rate of the product and neutral propellant through the highmechanical breakup spray head was approximately halved and the deliveryrate was then in the order of about one gram per second. This was verydesirable since a delivery rate of one gram per second was quiteadequate for application of a powdered anti-perspirant.

By reducing the delivery rate of a product such as a powderedanti-perspirant, the use life of product, product may be greatlyincreased as well as providing a safer product in which the user doesnot apply an amount of the product which might, in some cases, beactually harmful. In an anti-perspirant powder formulation, the activeingredient is aluminum chlorhydrate which is generally present inadmixture with a neutral cosmetic powder such as talc. The content ofaluminum chlorhydrate with respect to talc will be dependent upon theapplication rate of the product in the form of an aerosol spray. If theapplication rate is relatively high, the content of aluminumchlorhydrate may have to be reduced while the content of talc and otheringredients is increased to insure that the user does not injure himselfby applying too great an amount of aluminum chlorhydrate. Thus, eventhough aluminum chlorhydrate is the effective component, it may benecessary to supply the user with a larger quantity of inert materialsmerely as a safeguard to prevent injury.

A more satisfactory solution, which is made possible by the presentinvention through increasing the vapor pressure of the neutralpropellant, is to tailor the aerosol dispensing system to permit a lowerdifferential pressure across the flexible bag 16. The percentage of theactive ingredient in the overall formulation may then be increasedwithout running a danger of injury to the user through over applicationof the active ingredient. For example, when the delivery rate of productis cut in half, it may then be possible to double the content of theactive ingredient in the product. The product is, thus, a more effectiveproduct with longer use life than previous products that were dispensedat a relatively high delivery rate due to the make-up of the propellantdelivery system.

A still further result which follows from use of a reduced productdelivery rate is that the discharge of neutral propellant into theatmosphere during use of the propellant system is also reduced. Asstated previously, the quantity of neutral propellant which is requiredin any of the various product formulations of my aerosol dispensingsystem is markedly reduced as compared with the quantity of propellantgas that was discharged to the atmosphere in previous aerosol dispensingsystems where the primary gas was admixed directly with the product.However, even in the case of the present aerosol system, there is stillsome discharge of gas to the atmosphere along with discharge of theproduct. Thus, even in the case of the present system, it would bedesirable to reduce the discharge rate of neutral propellant to theatmosphere. By increasing the vapor pressure of the neutral propellantto a level of about 30 psig or higher, the content of neutral propellantin the aerosol product may be reduced while still obtaining a finelydivided aerosol spray. Also, the differential pressure across theflexible bag 16 may be reduced to reduce the delivery rate of theproduct and neutral propellant through the high mechanical breakup sprayhead.

By, thus, reducing the content of neutral propellant in the product andalso reducing the delivery rate of the product, a marked reduction inthe discharge rate of the neutral propellant to the atmosphere may beobtained during discharge of the aerosol product through the highmechanical breakup spray head. This is particularly desirable if ahalohydrocarbon is present either as a neutral propellant or as acomponent in a neutral propellant mixture since halohydrocarbons areconsidered to be potentially very harmful to mankind.

In defining a preferred vapor pressure under standard conditions for theneutral propellant, reference has bee made heretofore to a vaporpressure of about 30 psig or higher. While a neutral propellant having amuch higher vapor pressure than 30 psig, such as about 100 psig, may beused, such a neutral propellant would generally be impractical since itsuse would require a stronger container which would increase the cost ofthe overall system. For reasons of practicality, the neutral propellantwill, therefore, generally not have a vapor pressure in excess of about50 psig although there is no reason why a neutral propellant having ahigher vapor pressure could not be employed if the nature of the productwould justify the added cost of using a suitable high pressurecontainer.

With the increasing emphasis on environmental quality, it is conceivablethat at some future time the use of higher pressure aerosol containersmay be made practical by legislation which restricts the discharge ofvolatile solvents and the like into the atmosphere from aerosolproducts. If this should occur, a product, such as a frying pan oil,could then not be thinned by the inclusion of solvents and the fryingpan oil would have to be dispensed in a much more viscous state as anaerosol. This would then require the use of higher propellant pressuresand it would be economically feasible to discharge the more viscousproduct according to the present aerosol dispensing system through useof a neutral propellant having a much higher vapor pressure at standardconditions such as 100 psig.

In charging a barrier pack container with an aerosol system according tothe invention, the flexible inner bag 16 is preferably vacuum evacuatedand then charged with product. Following this, the neutral propellant ormixture of propellants is preferably charged to the second inner bag 16and the propellant is then charged to the propellant region between theflexible bag 16 and the rigid outer container 14. Preferably, the secondpropellant is charged after charging with the neutral propellant ormixture of propellants since the neutral propellant or mixture ofneutral propellants is easier to charge prior to charging with thepropellant. A method of charging a barrier pack container with anaerosol dispensing system according to the invention is disclosed in myprior .[.copending.]. application entitled "METHOD OF FILLING AN AEROSOLDISPENSING ARRANGEMENT" Ser. No. 466,306, filed May 2, 1974, nowabandoned, the subject matter of which is incorporated herein byreference.

As stated previously, the present aerosol dispensing system is admirablysuited for various products which cannot presently be dispensed as anaerosol, such as a vinyl latex or a vinyl-acrylic water base paint.Also, the aerosol dispensing system of the invention may be used withproducts, such as water base hair sprays, which may be dispersed as anaerosol through conventional aerosol systems. In the use of the presentaerosol dispensing system for a water base hair spray, the water contentof the hair spray may advantageously be reduced to provide a fine mistspray which is not as wet as existing aerosol hair spray formulations.The high water content of existing hair spray formulations is dictatedby parameters of existing aerosol dispensing systems which do not applyto the aerosol dispensing system of the invention. Thus, by using theaerosol dispensing system of the invention, the make-up of manyproducts, such as hair spray formulations, may now be radically alteredwhile providing the product as a fine spray. The present aerosoldispensing system, thus, makes possible a host of new aerosol productswhose make-up is not subject to the limitations imposed by previousaerosol dispensing systems in which the product was intermixed with arelatively large volume of a propellant that provided the driving forcefor expelling the product through a spray head.

As stated previously, a mechanical breakup spray head is an integralpart of the present aerosol dispensing system with the neutralpropellant or propellants being at least partially vaporized within thespray head. Many mechanical breakup spray heads are known and, ingeneral, these spray heads are characterized by the use of a swirlchamber within which the product is submitted to centrifugal forcebefore ejection of the product through an orifice into the atmosphere.In general, any of the various mechanical breakup spray heads may beused in the present aerosol dispensing system and the use of aparticular type of spray head is not required by the system.

I claim:
 1. An aerosol dispensing system comprising:an outer container;compressible inner container means positioned within said outercontainer; means to compress said inner container means positionedbetween said inner container means and said outer container; amechanical breakup spray head and valve assembly connected to said innercontainer means; .Iadd.said mechanical breakup spray head including adischarge orifice and a swirl chamber with the material being dischargedpassing through the swirl chamber and being subjected to centrifugalforce therein before being ejected through said discharge orifice;.Iaddend. a relatively non-foaming liquid product at a pressure aboveatmospheric pressure within said inner container means due to the forceexerted on the inner container means by said means to compress saidinner container means; a neutral propellant within said inner containermeans; said neutral propellant being in a liquid state at the pressurewithin said inner container means and being at least partially solubleor miscible in said liquid product, and said neutral propellant being atleast partially vaporized at atmospheric pressure or less on passage ofsaid product and neutral propellant through said spray head to create aturbulence within said spray head which produces breaking up of saidliquid product into a fine spray.
 2. The aerosol dispensing system ofclaim 1 wherein said liquid product is a water-base product, and saidneutral propellant is a hydrocarbon gas.
 3. The aerosol dispensingsystem of claim 2 wherein said neutral propellant propane.
 4. Theaerosol dispensing system of claim 2 wherein said neutral propellantcontains n-butane.
 5. The aerosol dispensing system of claim 2 whereinsaid neutral propellant contains isobutane.
 6. The aerosol dispensingsystem of claim 2 wherein said liquid product is a water-base paint. 7.The aerosol dispensing system of claim 1 wherein said liquid product isan ingestible food product, and said neutral propellant is a non-toxichydrocarbon or non-hydrocarbon gas.
 8. The aerosol dispensing system ofclaim 7 wherein said neutral propellant contains propane.
 9. The aerosoldispensing system of claim 7 wherein said neutral propellant containsn-butane.
 10. The aerosol dispensing system of claim 7 wherein saidneutral propellant contains isobutane.
 11. The aerosol dispensing systemof claim 1 includingsaid compressible inner container means being aflexible bag; a propellant region between said flexible bag and saidouter container; a second propellant in said propellant region, and saidsecond propellant exerting a differential pressure across said flexiblebag sufficient to eject said product and said neutral propellant throughsaid mechanical breakup spray head on opening of said valve assembly.12. The aerosol dispensing system of claim 1 wherein said neutralpropellant has a vapor pressure of about 30 psig at standard conditions.13. The aerosol dispensing system of claim 11 wherein said neutralpropellant has a vapor pressure of about 30 psig at standard conditions.14. A barrier pack aerosol dispensing system comprising:an outercontainer; a flexible inner container positioned within said outercontainer; a propellant region between said inner container and saidouter container; a mechanical breakup spray head and valve assemblyconnected to said inner container; .Iadd.said mechanical breakup sprayhead including a discharge orifice and a swirl chamber with the materialbeing discharged passing through the swirl chamber and being subjectedto centrifugal force therein before being ejected through said dischargeorifice; .Iaddend. a relatively non-foaming liquid product within saidinner container; a neutral propellant within said inner container; saidneutral propellant being in a liquid state within said inner containerand being at least partially soluble or miscible in said liquid product;a second propellant in said propellant region; said second propellantexerting a differential pressure across said inner container of at leastabout 30 psig sufficient to eject said product and said neutralpropellant through said mechanical breakup spray head on opening of saidvalve assembly; said neutral propellant being present in an amount ofabout 10 percent or less by volume of the volume of said product andsaid neutral propellant, and said neutral propellant being at leastpartially vaporized at atmospheric pressure or less on passage of saidproduct and neutral propellant through said spray head to create aturbulence within said spray head which produces breaking up of saidliquid product into a fine spray.
 15. The barrier pack aerosoldispensing system of claim 14 whereinsaid liquid product is a water-baseproduct, and said neutral propellant is a hydrocarbon gas.
 16. Thebarrier pack aerosol dispensing system of claim 15 wherein said neutralpropellant is propane.
 17. The barrier pack aerosol dispensing system ofclaim 15 wherein said neutral propellant is n-butane.
 18. The barrierpack aerosol dispensing system of claim 15 wherein said liquid productis a water-base paint.
 19. The barrier pack aerosol dispensing system ofclaim 14 whereinsaid liquid product is an ingestible food product, andsaid neutral propellant is a non-toxic hydrocarbon or non-hydrocarbongas.
 20. The barrier pack aerosol dispensing system of claim 19whereinsaid neutral propellant is propane.
 21. The barrier pack aerosoldispensing system of claim 19 whereinsaid neutral propellant isn-butane.
 22. The barrier pack aerosol dispensing system of claim 14whereinsaid neutral propellant is present in an amount of about 6percent by volume or less of the volume of said product and said neutralpropellant.
 23. The barrier pack aerosol dispensing system of claim 14including a surfactant in said liquid product in an amount sufficient toreduce the surface tension of said product to a level suitable fordispersion of said product as a spray of fine particles.
 24. The barrierpack aerosol dispensing system of claim 14 whereinsaid liquid product isan ingestible vegetable oil, and said neutral propellant is a non-toxichydrocarbon.
 25. The barrier pack aerosol dispensing system of claim 24wherein said neutral propellant is propane.
 26. The barrier pack aerosoldispensing system of claim 24 wherein said neutral propellant isn-butane.
 27. An aerosol dispensing system comprising:an outercontainer; compressible inner container means positioned within saidouter container; means to compress said inner container means positionedbetween said inner container means and said outer container; amechanical breakup spray head and valve assembly connected to said innercontainer means; .Iadd.said spray head including a discharge orifice anda swirl chamber with the material to be discharged passing through theswirl chamber and being subjected to centrifugal force therein beforebeing ejected through said discharge orifice; .Iaddend. a finely dividedpowder product at a pressure above atmospheric pressure within saidinner container means due to the force exerted on said inner containermeans by said means to compress said inner container means; a liquifiedneutral propellant within said inner container means; said neutralpropellant being present in an amount sufficient to form a slurry withsaid product and to carry said product into said spray head duringdischarge of said product, and said neutral propellant being at leastpartially vaporized at atmospheric pressure or less on passage of saidproduct and neutral propellant through said spray head to create aturbulence within said spray head which produces a fine powder spray.28. The aerosol dispensing system of claim 27 whereinsaid neutralpropellant is present in an amount ranging up to about 25 percent byweight or more of said product.
 29. The aerosol dispensing system ofclaim 27 includingsaid inner container means being a flexible bag; apropellant region between said flexible bag and said outer container; asecond propellant in said propellant region, and said second propellantexerting a differential pressure across said flexible bag sufficient toeject said product and said neutral propellant through said mechanicalbreakup spray head on opening of said valve assembly.
 30. The aerosoldispensing system of claim 27 wherein said neutral propellant a vaporpressure of about 30 psig at standard conditions.
 31. The aerosoldispensing system of claim 30 wherein said neutral propellant containspropane.
 32. The aerosol dispensing system of claim 30 wherein saidneutral propellant contains isobutane.
 33. The aerosol dispensing systemof claim 29 wherein said neutral propellant has a vapor pressure ofabout 30 psig at standard conditions.
 34. The aerosol dispensing systemof claim 33 wherein said neutral propellant contains propane.
 35. Theaerosol dispensing system of claim 33 wherein said neutral propellantcontains isobutane.